Method of manufacturing multilayer optical recording medium and multilayer optical recording medium

ABSTRACT

The method of manufacturing a multilayer optical recording medium according to this invention is a method of manufacturing a multilayer optical recording medium, having two recording layers deposited, with a spacer layer sandwiched therebetween, on a substrate (D 1 ) formed with a central mounting hole ( 1   a ). In forming the spacer layer between a second recording layer (L 1 ) and a first recording layer, the substrate (D 1 ) which has a fitting protrusion (D 1   a ) formed around the central mounting hole ( 1   a ) is fixed to a turntable ( 12 ) in a state where a center pin ( 12   c ) of the turntable ( 12 ) is inserted through the central mounting hole ( 1   a ). After a coating liquid (R) is dropped onto the substrate (D 1 ) at a predetermined location radially outward of the fitting protrusion (D 1   a ), the stamper ( 21 ) is placed over the substrate (D 1 ) while fitting a fitting groove ( 21   b ) and the fitting protrusion (D 1   a ) to each other. Then, the turntable ( 12 ) is caused to rotate to thereby spin-coat the coating liquid (R). This makes it possible to form the spacer layer without making the recording layers off-center.

TECHNICAL FIELD

[0001] This invention relates to a method of manufacturing a multilayeroptical recording medium having a plurality of recording layersdeposited with a spacer layer sandwiched therebetween, and a multilayerrecording medium.

BACKGROUND ART

[0002] The present applicant has developed a multilayer opticalrecording medium 31 shown in FIG. 14 as this kind of multilayer opticalrecording medium. This multilayer optical recording medium 31 has arecording layer L1, a spacer layer S, a recording layer L0, and a coverlayer C sequentially deposited on a disk-shaped substrate D11 having acentral mounting hole 1 a formed through a central portion thereof. Inthis multilayer optical recording medium 31, the recording layer L1 iscomprised of a reflective film for reflecting a laser beam set to arecording power and applied for recording and a laser beam set to areproducing power and applied for reproduction (each of which ishereinafter also simply referred to as “the laser beam” when it is notrequired to make a distinction between the two laser beams), a phasechange film whose optical reflectance is changed with a change in anoptical constant caused by application of the laser beam set to therecording power, and a protective film for protecting the phase changefilm, which are sequentially deposited on grooves and lands formed on asurface of the substrate D11. The spacer S is in the form of a thin filmmade of a light-transmissive resin such that it has a thickness ofapproximately 20 μm. On the other hand, the recording layer L0 iscomprised of a phase change film, a protective film, and the like,sequentially deposited on grooves and lands formed on a surface of thespacer layer S. The cover layer C, which is a layer that not onlyprotects the recording layer L0 from being scratched, but also functionsas a part of an optical path (lens), is in the form of a thin film madeof a light-transmissive resin. In the multilayer optical recordingmedium 31, the laser beam is applied in a direction indicated by anarrow A in FIG. 14, whereby recording of record data in the recordinglayers L0 and L1 or reading record data from the recording layers L0 andL1 is performed.

[0003] In manufacturing the multilayer optical recording medium 31,first, the recording layer L1 is formed on the substrate D11 e.g. by thesputtering method. Then, a coating liquid R is applied over therecording layer L1 by the spin coating method to thereby form the spacerlayer S. In doing this, as shown in FIG. 15, first, the substrate D11 isplaced on a base 12 a such that a center pin 12 c of a turntable 12 isinserted through the central mounting hole la of the substrate D11, withthe surface having the recording layer L1 formed thereon facing upward.In this case, the base 12 a is in the form of a disk with a flat uppersurface and connected to a motor, not shown, via a shaft 12 b. Further,during application of the coating liquid R, the turntable 12 is rotatedby the motor in a state where the substrate D11 having its radiallyinnermost portion (chucking area) sucked by negative pressure is placedthereon. Further, the center pin 12 c is a centering pin for aligningthe central portion of the substrate D11 and the central portion of theturntable 12, and erected on the central portion of the base 12 a, inthe form of a cylinder having a diameter slightly smaller than that ofthe central mounting hole 1 a, so as to facilitate mounting and removalof the substrate D11.

[0004] Next, the coating liquid R is dropped onto the substrate D11 fromthe tip of a nozzle 14 a, as shown in FIG. 16, with the turntable 12 inthe above-described state being rotated at a low speed. In doing this,the coating liquid R is dropped around the central mounting hole 1 a(onto the inner peripheral portion of the substrate D11). Then, theturntable 12 is rotated at a high speed to cause the coating liquid R tospread over the substrate D11 to the outer peripheral portion thereof.In doing this, the rotational speed of the turntable 12 and a timeperiod for maintaining high-speed rotation of the same are controlled asrequired, whereby the coating liquid R is radially moved from the innerperipheral portion to the outer peripheral position of the substrate D11by centrifugal force generated by the rotation of the turntable 12. Inthe meantime, superfluous part of the coating liquid R having reachedthe outer periphery of the substrate D11 flies off the substrate D11 bythe centrifugal force acting thereon. As a result, all area of thesurface of the substrate D11 is coated with a thin and substantiallyeven film of the coating liquid R as shown in FIG. 17.

[0005] Next, as shown in FIG. 18, a stamper 51 is placed over thesubstrate D11 having been coated with the coating liquid R, such thatthe center pin 12 c of the turntable 12 is inserted through a centralhole 21 a of the stamper 51. In this case, the stamper 51 is formed of amaterial capable of transmitting ultraviolet rays for curing the coatingliquid R, as described hereinafter. Further, the central hole 21 a isformed to have approximately the same diameter as that of the centralmounting hole 1 a. Furthermore, the stamper 51 has a lower surfacethereof subjected to treatment for forming asperities, such as grooves,lands, and pits, for the recording layer L0. Immediately after thesubstrate D11 has been coated, the coating liquid R still has fluidity.Therefore, the stamper 51 is placed on the coating liquid R, with thecoating liquid R conforming to the asperities of the stamper 51, i.e.the shapes of the grooves, the lands, and so forth. Then, ultravioletrays are applied to the substrate D11 in this state to cure the coatingliquid R, whereby the spacer layer S is completed. Subsequently, thestamper 51 is removed from the substrate D11 as shown in FIG. 19.Thereafter, the recording layer L0 is formed on the spacer layer S, andthen the cover layer C is formed by spin-coating the coating liquid Rover the recording layer L0 and curing the coating liquid. Thus, themanufacturing of the multilayer optical recording medium 31 iscompleted.

DISCLOSURE OF THE INVENTION

[0006] From the study of the above described method of manufacturing amultilayer optical recording medium 31, the present inventors found outthe following points for improvement: In this manufacturing method, thespacer layer S is formed by curing the coating liquid in a state wherethe stamper 51 is placed over the substrate D11 having been spin-coatedwith the coating liquid. In this case, as described hereinabove, thecenter pin 12 c of the turn table 12 is formed to have a diameterslightly smaller than that of the central mounting hole 1 a of thesubstrate D11 and that of the central hole 21 a of the stamper 51, so asto facilitate mounting and removal of the substrate D11 and the stamper51. Owing to this, slight gaps are formed between the rim of the centralmounting hole 1 a of the substrate D11 placed on the turntable 12 andthe peripheral surface of the center pin 12 c, and between the rim ofthe central hole 21 a of the stamper 51 placed over the substrate D11and the peripheral surface of the center pin 12 c. In this case, forexample, as shown in FIG. 18, if the substrate D11 and the stamper 51are placed on the turntable 12 in respective states deviated indifferent directions, the spacer layer S is formed in a state where thegrooves and lands on the recording layer L0 are misaligned from those onthe recording layer L1, causing eccentricity. Therefore, improvement inthis point is preferable.

[0007] On the other hand, as a method of reducing the eccentricity, itis contemplated to form the center pin 12 c such that it has anincreased diameter for being rather tightly fitted into the centralmounting hole 1 a of the substrate D11 and the central hole 21 a of thestamper 51. According to this method, it is possible to position thesubstrate D11 and the stamper 51 such that the central mounting hole laof the substrate D11 and the central hole 21 a of the stamper 51 arealigned with each other. However, while this method provides theimprovement of reduced eccentricity, there arises a problem of mountingand removal of the substrate D11 and the stamper 51 to and from thecenter pin 12 c. That is, it becomes difficult to fit the substrate D11on the center pin 12 c and remove the former from the latter. Thisbrings about the problem of markedly reduced productivity and increasedmanufacturing costs of the multilayer optical recording medium 31.

[0008] The present invention has been made to solve the above describedpoints for improvement, and a main object thereof is to provide a methodof manufacturing a multilayer optical recording medium, and a multilayeroptical recording medium-manufacturing apparatus, which are capable offorming a spacer layer without making recording layers off-center.

[0009] The method of manufacturing a multilayer optical recordingmedium, according to the present invention, is a method of manufacturinga multilayer optical recording medium having N recording layers (N is anatural number equal to or larger than 2) deposited, with a spacer layersandwiched therebetween, on a substrate having a central portion thereofformed with a central mounting hole, wherein in forming the spacer layerbetween an (M+1)-th recording layer (M is a natural number equal to orsmaller than (N−1)) and an M-th recording layer, as counted from anincident direction of a laser beam to be applied during reproduction ora laser beam to be applied during recording, the substrate which has asubstrate-side fitting portion formed around the central mounting holesuch that the substrate-side fitting portion can be fitted to astamper-side fitting portion formed on the stamper for forming the M-threcording layer, and the (M+1)-th recording layer formed thereon, isfixed to the turntable, in a state where a centering pin erected on acentral portion of the turntable is inserted through the centralmounting hole of the substrate; after a coating liquid for forming thespacer layer is dropped onto an upper surface of the substrate at apredetermined location radially outward of the substrate-side fittingportion, the stamper is placed over the substrate while fitting thestamper-side fitting portion and the substrate-side fitting portion toeach other; and then the turntable is caused to rotate to therebyspin-coat the coating liquid.

[0010] In this method of manufacturing an optical recording medium, informing the spacer layer between the (M+1)-th recording layer and theM-th recording layer, the substrate which has a substrate-side fittingportion formed around the central mounting hole is fixed to theturntable by inserting the centering pin of the turntable through thecentral mounting hole of the substrate, and after the coating liquid forforming the spacer layer is dropped at a predetermined location of thesubstrate radially outward of the substrate-side fitting portion, thestamper is placed over the substrate while fitting the stamper-sidefitting portion and the substrate-side fitting portion to each other.Then, the turntable is caused to rotate to thereby spin-coat the coatingliquid. This makes it possible to spin-coat the substrate with thecoating liquid in a state where the central portion of the substrate andthat of the stamper are aligned by fitting of the substrate-side fittingportion and the stamper-side fitting portion, and therefore, it ispossible to produce a non-defective multilayer optical recording mediumwithout making the recording layers off-center. Further, during drawingof the coating liquid, the substrate and the stamper can be keptparallel with each other, so that it is possible to make uniform thecoating thickness of the coating liquid in circumferential and radialdirections of the substrate.

[0011] The method of manufacturing a multilayer optical recordingmedium, according to the present invention, is a method of manufacturinga multilayer optical recording medium having N recording layers (N is anatural number equal to or larger than 2) deposited, with a spacer layersandwiched therebetween, on a substrate having a central portion thereofformed with a central mounting hole, wherein in forming the spacer layerbetween an (M+1)-th recording layer (M is a natural number equal to orsmaller than (N−1)) and an M-th recording layer, as counted from anincident direction of a laser beam to be applied during reproduction ora laser beam to be applied during recording, the substrate which has asubstrate-side fitting portion formed around the central mounting holesuch that the substrate-side fitting portion can be fitted to astamper-side fitting portion formed on the stamper for forming the M-threcording layer, and the (M+1)-th recording layer formed thereon, isfixed to the turntable, by inserting a centering pin erected on acentral portion of the turntable through the central mounting hole ofthe substrate; after a coating liquid for forming the spacer layer isdropped onto an upper surface of the substrate at a predeterminedlocation radially outward of the substrate-side fitting portion, theturntable is caused to rotate to thereby spin-coat the coating liquid;then the stamper is placed over the substrate while fitting thestamper-side fitting portion and the substrate-side fitting portion toeach other; and the coating liquid is cured in the resulting state.

[0012] In this method of manufacturing an optical recording medium, informing the spacer layer between the (M+1)-th recording layer and theM-th recording layer, the substrate which has a substrate-side fittingportion formed around the central mounting hole is fixed to theturntable by inserting the centering pin of the turntable through thecentral mounting hole of the substrate, and after the coating liquid forforming the spacer layer is dropped at a predetermined location of thesubstrate radially outward of the substrate-side fitting portion, theturntable is caused to rotate to thereby spin-coat the coating liquid.Then, in a state where the stamper has been placed over the substratewhile fitting the stamper-side fitting portion and the substrate-sidefitting portion to each other, and the coating liquid is cured. Thismakes it possible to cure the coating liquid in the state where thecentral portion of the substrate and the central portion of the stamperhave been aligned by fitting of the substrate-side fitting portion andthe stamper-side fitting portion when the stamper has been placed overthe stamper. Therefore, it is possible to produce a non-defectivemultilayer optical recording medium without making the recording layersoff-center.

[0013] In this case, it is preferred that an energy radiation-curableresin coating liquid is used as the coating liquid for forming thespacer layer, and a stamper formed of an energy radiation-transmissivematerial is used as the stamper. This makes it possible to form thespacer layer in a shorter time period compared with a method using athermosetting resin which is cured by application of heat. As a result,it is possible to sufficiently reduce the manufacturing costs of themultilayer optical recording medium.

[0014] Further, it is preferred that one of the stamper-side fittingportion and the substrate-side fitting portion is formed by a fittingprotrusion having an annular shape in plan view and the other thereof isformed by a fitting groove formed to be capable of being fitted on thefitting protrusion. This facilitates the operation of fitting thestamper-side fitting portion and the substrate-side fitting portion whenthe stamper is placed over the stamper. Further, by forming thesubstrate-side fitting portion as a fitting protrusion having an annularshape in plan view, it is possible to prevent the coating liquid droppedonto the substrate from flowing into the central mounting hole. As aresult, it is possible to prevent the coating liquid from being attachedto the chucking area.

[0015] The multilayer optical recording medium according to the presentinvention is a multilayer optical recording medium manufactured by themethod of manufacturing a multilayer optical recording medium accordingto the present invention, wherein the substrate-side fitting portion isformed on the substrate. With this arrangement, it is possible to formthe spacer layer in a state where the central portion of the substrateand that of the stamper have been aligned by fitting of thesubstrate-side fitting portion and the stamper-side fitting portion whenthe stamper is placed on the substrate during manufacturing of themultilayer optical recording medium. Therefore, it is possible toproduce a non-defective multilayer optical recording medium in which an(M+1)-th recording layer and an M-th recording layer are prevented frombeing off-center.

[0016] It should be noted that the present disclosure relates to thesubject matter included in Japanese Patent Application No. 2001-308111filed on Oct. 4, 2001, and it is apparent that all the disclosurestherein are incorporated herein by reference.

BRIEF DESCRIPTION OF DRAWINGS

[0017]FIG. 1 is a side cross-sectional view of a multilayer opticalrecording medium 1 according to an embodiment of the present invention,in its completely manufactured state;

[0018]FIG. 2 is a block diagram showing the configuration of a coatingapparatus 11 according to an embodiment of the present invention;

[0019]FIG. 3 is a perspective view of the appearance of a turntable 12of the coating apparatus 11;

[0020]FIG. 4 is a side cross-sectional view of a state of a substrate D1having been placed on the turntable 12;

[0021]FIG. 5 is a side cross-sectional view-of a state of a coatingliquid R having been dropped onto the substrate D1 on the turntable 12;

[0022]FIG. 6 is a side cross-sectional view of a state of a stamper 21having been moved to a location above the substrate D1 in the FIG. 5state;

[0023]FIG. 7 is a side cross-sectional view of the stamper 21 placed onthe substrate D1 in the FIG. 6 state;

[0024]FIG. 8 is a side cross-sectional view of a state of the coatingliquid R between the substrate D1 and the stamper 21 having reached theouter periphery of the substrate D1;

[0025]FIG. 9 is a side cross-sectional view of a state of the stamper 21having been removed from the substrate D1 having a spacer layer S formedthereon;

[0026]FIG. 10 is a side cross-sectional view of a substrate D2 and astamper 22 according to another embodiment of the present invention;

[0027]FIG. 11 is a side cross-sectional view of a multilayer opticalrecording medium 2 according to the embodiment of the present invention,in its completely manufactured state;

[0028]FIG. 12 is a side cross-sectional view of a substrate D3 and astamper 23 according to another embodiment of the present invention;

[0029]FIG. 13 is a side cross-sectional view of a multilayer opticalrecording medium 3 according to the embodiment of the present invention,in its completely manufactured state;

[0030]FIG. 14 is a side cross-sectional view of a multilayer opticalrecording medium 31 in its completely manufactured state;

[0031]FIG. 15 is a side cross-sectional view of a state of a substrateD11 having been placed on a turntable 12;

[0032]FIG. 16 is a side cross-sectional view of a state of the coatingliquid R having been dropped onto the substrate D11 on the turntable 12;

[0033]FIG. 17 is a side cross-sectional view of a state of the coatingliquid R having reached the outer periphery of the substrate D11;

[0034]FIG. 18 is a side cross-sectional view of a state of a stamper 51having been placed over the substrate D11 in the FIG. 14 state; and

[0035]FIG. 19 is a side cross-sectional view of a state of the stamper51 having been removed from the substrate D11 having a spacer layer Sformed thereon.

BEST MODE FOR CARRYING OUT THE INVENTION

[0036] Hereinafter, preferred embodiments of a method of manufacturing amultilayer optical recording medium and a multilayer recording medium,according to the present invention, will be described with reference tothe accompanying drawings.

[0037] First of all, the structure of the multilayer optical recordingmedium 1 will be described with reference to FIG. 1.

[0038] The multilayer optical recording medium 1 is constructed bysequentially depositing a recording layer L1 corresponding to an(M+1)-th (M=1) recording layer in the present invention, a spacer layerS, a recording layer L0 corresponding to an M-th (M=1) recording layerin the present invention, and a cover layer C, on a substrate D1, suchthat record data can be read or recorded by applying a laser beam set toa reproducing power or a laser beam set to a recording power, onto themultilayer optical recording medium 1 from a cover layer C side in adirection indicated by an arrow A in FIG. 1. The substrate D1 is formedby injection molding such that it is disk-shaped (flat plate-shaped)with an overall diameter of approximately 120 mm. Further, the substrateD1 has a central portion thereof formed with a central mounting hole lahaving a diameter of approximately 15 mm, for use when the substrate D1is mounted in a recording and reproducing apparatus. Further, thesubstrate D1 is formed with an annular chucking area having a width ofapproximately 10 mm, at a location outward of the central mounting hole1 a, such that the upper surface (chucking surface) of the chucking areais flush with the upper surface of the cover layer C. Further, the outerperipheral portion of the chucking surface is formed with a fittingprotrusion D1 a which corresponds to a substrate-side fitting portion inthe present invention, and formed by causing a portion of the substrateD1 to protrude such that the protruded portion has a ring-like (annular)shape in plan view. Further, radially outward of the fitting protrusionD1 a, there are formed grooves, lands, and pits for the recording layerL1. The recording layer L1 is formed by forming a reflective film, aphase change film, and a protective film, on the substrate D1 by thesputtering method. The spacer layer S is formed on the recording layerL1 using a light-transmissive coating liquid R, such that it has athickness of approximately 20 μm. Further, grooves, lands, and pits forforming the recording layer L0 are formed on the surface of the spacerlayer S, by a stamper 21, as will be described hereinafter. Therecording layer L0 is formed by forming a phase change film, aprotective film, and the like, on the spacer layer S by the sputteringmethod. Further, the cover layer C is formed of a light transmissivematerial such that it has a thickness of approximately 90 μm.

[0039] On the other hand, the stamper 21 is a resin stamper or a glassstamper as a dedicated jig for manufacturing the multilayer opticalrecording medium 1, which has a surface thereof subjected towater-repelling treatment, such as fluorine treatment or siliconetreatment. As shown in FIG. 6, the stamper 21 is in the form of a diskmade of a material capable of transmitting ultraviolet rays (energyradiation) for curing the coating liquid R. Further, further, an innerperipheral portion of a lower surface of the stamper 21 is formed with afitting groove (stamper-side fitting portion) 21 b having a ring-like(annular) shape in plan view, for having the fitting protrusion D1 a ofthe substrate D1 fitted therein, and a part radially outward of thefitting groove 21 b is subjected to treatment for forming asperities,such as grooves, lands, and pits, for the recording layer L0. In view ofreleasability from the spacer layer S, it is preferable that of all thesurfaces of the spacer 21, at least the surface formed with the grooves,lands, and pits is subjected to surface treatment, such as fluorinetreatment, and it is further preferable that the surface is formed of anamorphous cyclic polyolefin resin having an excellent releasability froman energy radiation curable resin. Further, the stamper 21 has a centralportion thereof formed with a central hole 21 a having approximately thesame diameter as that of the central mounting hole la of the substrateD.

[0040] Next, the arrangement of the multilayer optical recordingmedium-manufacturing apparatus for manufacturing a multilayer opticalrecording medium by the method of manufacturing a multilayer opticalrecording medium, according to the present invention, will be describedwith reference to FIGS. 2 and 3.

[0041] The coating apparatus 11, which is the multilayer opticalrecording medium-manufacturing apparatus, forms the spacer layer S byapplying the coating liquid R over the substrate D1 and then curing thesame, when the multilayer optical recording medium 1 is manufactured. Asshown in FIG. 2, the coating apparatus 11 is comprised of a turntable12, a motor 13, a coating liquid supply section 14, a vertical movementmechanism 15, an ultraviolet ray irradiation section 16 and a controlsection 17. As shown in FIG. 3, the turntable 12 is comprised of adisk-shaped base 12 a having a flat upper surface such that thesubstrate D1 can be placed thereon, a shaft 12 b connected to the centerof the lower surface of the base 12 a and connected to the rotationalshaft of the motor 13, and a center pin 12 c erected on a centralportion of the upper surface of the base 12 a. In this case, the centerpin 12 c is in the form of a cylinder with a diameter slightly smallerthan that of the central mounting hole 1 a of the substrate D1, and hasa periphery of the top thereof chamfered such that the center pin 12 ccan be easily inserted into the central mounting hole 1 a of thesubstrate D1. It should be noted that the turntable 12 is not limited tothe configuration in which the upper surface thereof is flat, but may beconfigured such that protrusions are firmed respectively on the mostinner peripheral and the most outer peripheral portions of the uppersurface of the turntable 12 along the circumference thereof, and thesubstrate D1 is placed on the protrusions, to thereby prevent thesubstrate D1 from being scratched by contact or otherwise. Further, theturntable 12 has a plurality of suction ports H, H, . . . , formed atrespective locations opposed to the chucking area of the substrate D1.Accordingly, when the coating liquid R is applied, air below thesubstrate D1 is sucked by an air pump (not shown) via the suction portsH, H, . . . , whereby the substrate D1 is attracted toward the turntable12. It should be noted that since the air pump for sucking the substrateD1 is known, illustration in figures and detailed description thereofare omitted.

[0042] The motor 13 is controllably driven by the control section 17 torotate the turntable 12. The coating liquid supply section 14, whichforms a coating liquid-dropping section together with the nozzle 14 a,drops the coating liquid R for forming the spacer layer S onto thesubstrate D1 via the nozzle 14 a under the control of the controlsection 17. In this process, the nozzle 14 a is moved upward anddownward with respect to the substrate D1 by-a vertical movementmechanism, not shown. The vertical movement mechanism 15 places thestamper 21 on the substrate D1 under the control of the control section17. The ultraviolet ray irradiation section 16 emits ultraviolet raystoward the substrate D1 under the control of the control section 17 tothereby cure the coating liquid R having applied over the surface of thesubstrate D1. The control section 17 controllably drives the motor 13,the coating liquid supply section 14, the vertical movement mechanism15, and the ultraviolet ray irradiation section 16.

[0043] Next, the method of manufacturing the multilayer opticalrecording medium 1 will be described with reference to drawings.

[0044] First, the recording layer L1 is formed on the substrate D1 e.g.by the sputtering method. Then, the spacer layer S is formed by applyingthe coating liquid R onto the recording layer L1. More specifically,first, the substrate D1 is placed on the turntable 12 with the surfacehaving the recording layer L1 formed thereon facing upward, as shown inFIG. 4. In doing this, the center pin 12 c is inserted through thecentral mounting hole la of the substrate D1. In this case, since thecenter pin 12 c is formed to have a cylindrical shape having a smallerdiameter than the central mounting hole 1 a of the substrate D1 asdescribed above, it is easy to insert the center pin 12 c through thecentral mounting hole 1 a. Then, the control section 17 drives the airpump, not shown, whereby the substrate D1 having the center pin 12 cinserted therethrough is sucked toward the turntable 12. Thus, thesubstrate D1 is fixed onto the turntable 12.

[0045] Next, the control section 17 controllably drives the motor 13 tothereby cause the turntable 12 to rotate at a rotational speed e.g. ofapproximately 50 rpm. Then, the control section 17 causes the nozzle 14a to move downward and controllably drives the coating liquid supplysection 14 to supply the coating liquid R to the nozzle 14 a. At thistime, the tip of the nozzle 14 a is positioned at a location radiallyoutward of the fitting protrusion D1 a. Then, due to the supply of thecoating liquid R by the coating liquid supply section 14, the coatingliquid R is dropped from the tip of the nozzle 14 a onto the substrateD1, as shown in FIG. 5. At this time, the coating liquid is dropped to alocation from which it can be naturally spread toward the innerperipheral portion of the substrate D1 by having the stamper 21 placedover the substrate D1 afterwards to completely fill the space at theinner peripheral portion thereof (space defined by the upper surface ofthe substrate D1, the lower surface of the stamper 21, and peripheralsurface of the fitting protrusion D1 a). By thus dropping the coatingliquid R, it is possible to prevent formation of a remaining space, andfurthermore, effectively prevent the coating thickness from being madenon-uniform due to a high-speed rotation of the turn table 12. Further,in this state, the coating liquid R has some degree of viscosity, andhence, immediately after being dropped from the nozzle 14 a, the coatingliquid R is positioned in the vicinity of the fitting protrusion D1 a onthe substrate D1 and has an annular shape in top view. In this case,since the fitting protrusion D1 a has an annular shape in plan view, andthe central mounting hole la is surrounded by the fitting protrusion D1a, so that the dropped coating liquid R on the substrate D1 is held fromflowing into the central mounting hole 1 a, whereby the coating liquid Ris prevented from being attached to the chucking area.

[0046] Then, after causing the nozzle 14 a to move upward, the controlsection 17 controllably drives the vertical movement mechanism 15 tomove the stamper 21 to a location above the substrate D1, as shown inFIG. 6. Then, as shown in FIG. 7, the control section 17 controllablydrives the vertical movement mechanism 15 to place the stamper 21 overthe substrate D1. In doing this, the vertical movement mechanism 15moves the stamper 21 downward while positioning the stamper 21 such thatthe center pin 12 c is inserted through the central hole 21 a of thestamper 21. This causes the center pin 12 c to be inserted into thecentral hole 21 a and at the same time causes the fitting protrusion D1a of the substrate D1 to be fitted into the fitting groove 21 b. At thistime, since both the fitting protrusion D1 a and the fitting groove 21 bare formed to have respective annular shapes in plan view, the fittingprotrusion D1 a and the fitting groove 21 b can be easily fitted only bymoving the stamper 21 downward. Further, due to the fitting of thefitting protrusion D1 a and the fitting groove 21 b, the central portionof the substrate D1 and the central portion of the stamper 21 arealigned with the substrate D1 and the stamper 21 being held parallelwith each other. Further, when the stamper 21 moved downward is broughtinto contact with the coating liquid R, the coating liquid R is firstbrought into line contact with the lower surface of the stamper 21, andthen gradually brought into surface contact therewith. Further, as thestamper 21 is further pushed downward, the coating liquid R is graduallyspread toward the outer periphery of the substrate D1 while conformingto the lower surface of the stamper 21.

[0047] Then, the control section 17 causes the rotational speed of themotor 13 to be increased to thereby increase the rotational speed of theturntable 12 to e.g. approximately 1000 rpm. This increases thecentrifugal force applied to the coating liquid R, and hence, as shownin FIG. 8, the coating liquid R is rapidly spread between the substrateD1 and the stamper 21 toward the outer periphery of the substrate D1. Inthis process, the coating liquid R is rapidly spread (drawn), with analmost perfectly circular shape of the outline thereof in plan viewbeing maintained, while conforming to the upper surface of the substrateD1 and the lower surface of the stamper 21. Further, as the coatingliquid R is drawn, the thickness of the coating liquid R is reduced, andhence the stamper 21 performs translation (downward motion) toward thesubstrate D by the decreased amount of thickness of the coating liquidR. Therefore, by controlling the rotational speed of the motor 13 andthe time period for maintaining high-speed rotation of the same, i.e. bycontrolling a shake-off amount of the coating liquid R, it is possibleto accurately control the coating thickness of the coating liquid R(film thickness of the spacer layer S) to a target value. It should benoted that in this case, the substrate D and the stamper 21 are heldparallel with each other by centrifugal force acting on both of them. Atthe same time, since the fitting protrusion D1 a of the substrate D1 isfitted in the fitting groove 21 b of the stamper 21, the respectivecentral portions of the substrate D1 and the stamper 21 are maintainedin the aligned state. As a result, the coating thickness of the coatingliquid R along the circumference of the substrate D1 becomes uniform.

[0048] In the meantime, superfluous part of the coating liquid R havingreached the radially outermost portion of the substrate D1 flies off thesubstrate D1 by the centrifugal force acting on the substrate D1. As aresult, a layer of the coating liquid R almost uniformly applied ontothe substrate D1 from the inner periphery to the outer periphery to thetarget thickness is formed between the substrate D1 and the stamper 21.Then, the ultraviolet ray irradiation section 16 irradiates thesubstrate D1 with ultraviolet rays under the control of the controlsection 17. As a result, the coating liquid R is cured by theultraviolet rays applied through the stamper 21, whereby formation ofthe spacer layer S is completed. Then, the control section 17 carriesout stop control of the motor 13 to stop the rotation of the turntable12. Next, after stopping the air pump, the substrate D1 is removed fromthe turntable 12. At this time, since the center pin 12 c is formed tohave a diameter smaller than that of the central mounting hole 1 a, thesubstrate D1 is easily removed. Then, the stamper 21 is removed from thesubstrate D1 as shown in FIG. 9. Thereafter, the recording layer L0 isformed on the spacer layer S, and then the cover layer C is formed byspin-coating the recording layer L0 with a coating liquid and curing thecoating liquid on the recording layer L0. In doing this, the cover layerC is formed on the recording layer L0 such that the upper surface of thechecking area is flush with the upper surface of the cover layer C, asdescribed hereinbefore. This completes the manufacturing of themultilayer optical recording medium 1 shown in FIG. 1.

[0049] As described above, according to the coating apparatus 11, byproviding the fitting groove 21 b in the stamper 21, and at the sametime, providing the fitting protrusion D1 a which can be fitted in thefitting groove 21 b, on the substrate D1, the fitting protrusion D1 a isfitted into the fitting groove 21 b when the stamper 21 is placed overthe substrate D1 coated with the coating liquid R, which makes itpossible to form the space layer S in a state where the central portionof the substrate D1 and the central portion of the stamper 21 arealigned. Therefore, it is possible to produce a non-defective multilayeroptical recording medium without making the recording layers L0 and L1off-center. Further, when the coating liquid R is drawn, since thefitting protrusion D1 a and the fitting groove 21 b have been fittedwith each other, the substrate D1 and the stamper 21 are held parallelwith each other, so that the coating thickness of the coating liquid Rcan be made uniform in circumferential and radial directions of thesubstrate D1. Further, according to this multilayer optical recordingmedium 1, the fitting protrusion D1 a slightly protrudes from the outerperipheral portion of the chucking area, which makes it possible toeffectively prevent the disk surface from being scratched when themultilayer optical recording media 1 are stacked one upon another.

[0050] It should be noted that the present invention is by no meanslimited to the aforementioned embodiment but it can be modified asrequired. For example, the substrate D1 is not limited to the diskshape, but there may be employed any of substrates having variousshapes. Further, although the embodiment of the present invention hasbeen described based on the respective examples of the substrate D1 andthe stamper 21 which have the fitting protrusion D1 a and the fittinggroove 21 b, respectively, both annular in plan view, the presentinvention is not limited to this, but may be configured such that two ormore, preferably three or more pin-shaped fitting protrusions areerected on one of the upper surface of the substrate and the lowersurface of the stamper, and fitting recesses into which these pin-shapedfitting protrusions can be fitted are formed in the other of the uppersurface of the substrate and the lower surface of the stamper, therebyenabling the substrate and the stamper to be aligned. Further, in placeof the pin-shaped fitting protrusions, arcuate fitting protrusions maybe formed in one of the upper surface of the substrate and the lowersurface of the stamper, and arcuate fitting recesses into which thesearcuate fitting protrusions can be fitted may be formed in the other ofthe upper surface of the substrate and the lower surface of the stamper.Further, although the embodiment of the present invention has beendescribed based on the example of the fitting groove 21 b being formedin the stamper 21 side and the fitting protrusion D1 a being formed onthe substrate D1 side, the present invention is not limited to this, butas in the case of a stamper 22 and a substrate D2 shown in FIG. 10, afitting protrusion 22 b may be formed on the stamper 22 side and afitting groove D2 a may be formed on the substrate D2 side. When thisconfiguration is employed, a multilayer optical recording medium shownin FIG. 11 is produced. It should be noted that in the arrangementillustrated in FIGS. 10 and 11, elements thereof identical to those ofthe multilayer optical recording medium 1 and the apparatus formanufacturing the same are designated by identical numerals, and aduplicate description thereof is omitted.

[0051] Further, as in the case of a multilayer optical recording medium3 shown in FIG. 13, all or part of the chucking area may be formed as anannular fitting protrusion (substrate-side fitting portion) D3 a. Inmanufacturing this multilayer optical recording medium 3, as shown inFIG. 12, a stamper 23 is employed which has a fitting recess(stamper-side fitting portion) 23 b formed around the central mountinghole 21 a thereof, and the fitting recess 23 b and the fittingprotrusion D3 a of the substrate D3 are fitted to each other, whereby itis possible to manufacture a non-defective optical recording medium 3with the respective upper surfaces of the chucking area and the coverlayer C being flush with each other, without making the recording layersL0 and L1 off-center. It should be noted that in the arrangementillustrated in FIGS. 11 to 13, elements thereof identical to those ofthe multilayer optical recording medium 1 and the apparatus formanufacturing the same are designated by identical numerals, and aduplicate description thereof is omitted.

[0052] Further, although the embodiment of the present invention hasbeen described based on based on the example in which after completingdropping of the coating liquid R, the stamper 21 is placed over thesubstrate D1, and then the turn table 12 is rotated at a high speed tothereby spin-coat the coating liquid R, this is not limitative, butafter completing spin-coating of the coating liquid R over the surfaceof the substrate D1, the stamper 21 can be placed over the substrate D1while fitting the fitting groove 21 b and the fitting protrusion D1 a toeach other. In this manufacturing method as well, similarly to themanufacturing method described hereinabove, when the stamper 21 isplaced over the substrate D1, the fitting protrusion D1 a is fitted inthe fitting groove 21 b to align the substrate D1 and the stamper 21,whereby it is possible to produce non-defective multilayer opticalrecording medium without making the recording layers L0 and L1off-center. Further, in the above-described embodiment of the presentinvention, the multilayer optical recording medium 1 having tworecording layers L1 and L0 has been described by way of example, this isnot limitative, but the method of manufacturing a multilayer opticalrecording medium according to the present invention can be effectivelyapplied to manufacturing of a multilayer optical recording medium havingthree or more recording layers.

[0053] Furthermore, although in the embodiment of present invention, therecording layers L0 and L1 each having a phase change film are describedby way of example, the recording layers in the present invention are notlimited to these, but they may be in the form of recording layers eachhaving a thin film of a dye-based resin, for example. Further, thepresent invention can be applied to the manufacturing of a ROM havingthe recording layers L0 and L1 in which information is recorded inadvance by forming pits.

[0054] Industrial Applicability

[0055] As described hereinbefore, the method of manufacturing amultilayer optical recording medium, according to the present invention,is a method of manufacturing a multilayer optical recording mediumhaving N recording layers (N is a natural number equal to or larger than2) deposited, with a spacer layer sandwiched therebetween, on asubstrate having a central portion thereof formed with a centralmounting hole, wherein in forming the spacer layer between an (M+1)-threcording layer (M is a natural number equal to or smaller than (N−1))and an M-th recording layer, as counted from an incident direction of alaser beam to be applied during reproduction or a laser beam to beapplied during recording, the substrate which has a substrate-sidefitting portion formed around the central mounting hole such that thesubstrate-side fitting portion can be fitted to a stamper-side fittingportion formed on the stamper for forming the M-th recording layer, andthe (M+1)-th recording layer formed thereon, is fixed to the turntable,in a state where a centering pin erected on a central portion of theturntable is inserted through the central mounting hole of thesubstrate; after a coating liquid for forming the spacer layer isdropped onto an upper surface of the substrate at a predeterminedlocation radially outward of the substrate-side fitting portion, thestamper is placed over the substrate while fitting the stamper-sidefitting portion and the substrate-side fitting portion to each other;and then the turntable is caused to rotate to thereby spin-coat thecoating liquid. This makes it possible to spin-coat the substrate withthe coating liquid in a state where the central portion of the substrateand that of the stamper are aligned by fitting of the substrate-sidefitting portion and the stamper-side fitting portion, and therefore, itis possible to produce a non-defective multilayer optical recordingmedium without making the recording layers off-center. Further, duringdrawing of the coating liquid, the substrate and the stamper can be keptparallel with each other, so that it is possible to make uniform thecoating thickness of the coating liquid in circumferential and radialdirections of the substrate. This realizes the method of manufacturing amultilayer optical recording medium, which is capable of forming aspacer layer without making the respective recording layers off-center.

1. A method of manufacturing a multilayer optical recording mediumhaving N recording layers (N is a natural number equal to or larger than2) deposited, with a spacer layer sandwiched therebetween, on asubstrate having a central portion thereof formed with a centralmounting hole, wherein in forming the spacer layer between an (M+1)-threcording layer (M is a natural number equal to or smaller than (N−1))and an M-th recording layer, as counted from an incident direction of alaser beam to be applied during reproduction or a laser beam to beapplied during recording, the substrate which has a substrate-sidefitting portion formed around the central mounting hole such that thesubstrate-side fitting portion can be fitted to a stamper-side fittingportion formed on the stamper for forming the M-th recording layer, andthe (M+1)-th recording layer formed thereon, is fixed to the turntable,in a state where a centering pin erected on a central portion of theturntable is inserted through the central mounting hole of thesubstrate; after a coating liquid for forming the spacer layer isdropped onto an upper surface of the substrate at a predeterminedlocation radially outward of the substrate-side fitting portion, thestamper is placed over the substrate while fitting the stamper-sidefitting portion and the substrate-side fitting portion to each other;and then the turntable is caused to rotate to thereby spin-coat thecoating liquid.
 2. A method of manufacturing a multilayer opticalrecording medium having N recording layers (N is a natural number equalto or larger than 2) deposited, with a spacer layer sandwichedtherebetween, on a substrate having a central portion thereof formedwith a central mounting hole, wherein in forming the spacer layerbetween an (M+1)-th recording layer (M is a natural number equal to orsmaller than (N−1)) and an M-th recording layer, as counted from anincident direction of a laser beam to be applied during reproduction ora laser beam to be applied during recording, the substrate which has asubstrate-side fitting portion formed around the central mounting holesuch that the substrate-side fitting portion can be fitted to astamper-side fitting portion formed on the stamper for forming the M-threcording layer, and the (M+1)-th recording layer formed thereon, isfixed to the turntable, by inserting a centering pin erected on acentral portion of the turntable through the central mounting hole ofthe substrate; after a coating liquid for forming the spacer layer isdropped onto an upper surface of the substrate at a predeterminedlocation radially outward of the substrate-side fitting portion, theturntable is caused to rotate to thereby spin-coat the coating liquid;then the stamper is placed over the substrate while fitting thestamper-side fitting portion and the substrate-side fitting portion toeach other; and the coating liquid is cured in the resulting state.
 3. Amethod of manufacturing a multilayer optical recording medium, asclaimed in claim 1, wherein an energy radiation-curable resin coatingliquid is used as the coating liquid for forming the spacer layer, and astamper formed of an energy radiation-transmissive material is used asthe stamper.
 4. A method of manufacturing a multilayer optical recordingmedium, as claimed in claim 2, wherein an energy radiation-curable resincoating liquid is used as the coating liquid for forming the spacerlayer, and a stamper formed of an energy radiation-transmissive materialis used as the stamper.
 5. A method of manufacturing a multilayeroptical recording medium, as claimed in claim 1, wherein one of thestamper-side fitting portion and the substrate-side fitting portion isformed by a fitting protrusion having an annular shape in plan view andthe other thereof is formed by a fitting groove formed to be capable ofbeing fitted on the fitting protrusion.
 6. A method of manufacturing amultilayer optical recording medium, as claimed in claim 2, wherein oneof the stamper-side fitting portion and the substrate-side fittingportion is formed by a fitting protrusion having an annular shape inplan view and the other thereof is formed by a fitting groove formed tobe capable of being fitted on the fitting protrusion.
 7. A method ofmanufacturing a multilayer optical recording medium, as claimed in claim3, wherein one of the stamper-side fitting portion and thesubstrate-side fitting portion is formed by a fitting protrusion havingan annular shape in plan view and the other thereof is formed by afitting groove formed to be capable of being fitted on the fittingprotrusion.
 8. A method of manufacturing a multilayer optical recordingmedium, as claimed in claim 4, wherein one of the stamper-side fittingportion and the substrate-side fitting portion is formed by a fittingprotrusion having an annular shape in plan view and the other thereof isformed by a fitting groove formed to be capable of being fitted on thefitting protrusion.
 9. A multilayer optical recording mediummanufactured by the method of manufacturing a multilayer opticalrecording medium as claimed in claim 1, wherein the substrate-sidefitting portion is formed on the substrate.
 10. A multilayer opticalrecording medium manufactured by the method of manufacturing amultilayer optical recording medium as claimed in claim 2, wherein thesubstrate-side fitting portion is formed on the substrate.
 11. Amultilayer optical recording medium manufactured by the method ofmanufacturing a multilayer optical recording medium as claimed in claim3, wherein the substrate-side fitting portion is formed on thesubstrate.
 12. A multilayer optical recording medium manufactured by themethod of manufacturing a multilayer optical recording medium as claimedin claim 4, wherein the substrate-side fitting portion is formed on thesubstrate.
 13. A multilayer optical recording medium manufactured by themethod of manufacturing a multilayer optical recording medium as claimedin claim 5, wherein the substrate-side fitting portion is formed on thesubstrate.
 14. A multilayer optical recording medium manufactured by themethod of manufacturing a multilayer optical recording medium as claimedin claim 6, wherein the substrate-side fitting portion is formed on thesubstrate.
 15. A multilayer optical recording medium manufactured by themethod of manufacturing a multilayer optical recording medium as claimedin claim 7, wherein the substrate-side fitting portion is formed on thesubstrate.
 16. A multilayer optical recording medium manufactured by themethod of manufacturing a multilayer optical recording medium as claimedin claim 8, wherein the substrate-side fitting portion is formed on thesubstrate.